Windows MR was deprecated and cannot run on the newest version of Windows; running older versions of Windows will only have support for it through to ~2026. It's very unfortunate that it's not long for this world because I hear the HP Reverb G2 is still a great headset.
Edit: If you're looking for a cheap headset, the best option is usually on Craigslist/Marketplace. Used first-generation headsets (meaning the two Oculus Rift models, early HTC headsets) which are still in perfectly workable condition go for only $100-$200.
Definitely seeing some people complain about the design changes; once my server updates I'm sure I'll see for myself. But for the most part I'm fairly pleased with the new notification grouping. Long strings of hundreds of people liking the same post over and over meant I missed replies sometimes.